Critical dimension scanning electron microscopes (CD-SEMs) and Dual Beam Focused Ion Beam SEMs (FIB) are often used to analyze and provide measurement of sub-micron features in surface and cross-sections of the read and write heads of a magnetic transducer in magnetic hard disk drives. A group of sliders including read/write heads may be arranged in a fixture called a rowbar holder, and from there, the sliders may be transferred onto an adhesive strip on a wafer for analysis in the CD-SEM and FIB. When testing head sliders in a high throughput automated metrology CD-SEM and FIB tool, it is important to precisely align ends of the sliders including the deposited read and write head film layers along a reference datum. If the high throughput CD-SEM or FIB encounters a misaligned head slider, it may be unable to automatically progress analysis of features of the succeeding slider's read/write layers, requiring stoppage of the metrology test while a technician manually re-teaches position reference in the application software on misaligned sliders and then resumes the automated testing run. High throughput CD-SEMs and FIBs are expensive tools to run, and any unexpected work stoppage to re-teach misaligned sliders can be costly.
A problem with conventional slider testing as explained above is that the dimensions of head sliders can vary slightly due to manufacturing tolerances. Thus, when clamped within a rowbar holder, the deposited end of some sliders may rest properly against the reference datum, but smaller sliders may rotate slightly, or otherwise have deposited ends which are not flush against the reference datum. In practice, this happens to more than 80% of sliders. This large incidence of misaligned sliders is resulting in an unacceptably high rate of work stoppages during CD-SEM and FIB testing.